Treatment of fluorocarbon feedstocks

ABSTRACT

A method of treating a fluorocarbon feedstock includes heating, by means of radio frequency induction, a heating zone to a high temperature, allowing a fluorocarbon feedstock, comprising at least one fluorocarbon compound, to heat up in the heating zone so that the fluorocarbon compound dissociates into at least one fluorocarbon precursor or reactive species, and cooling the fluorocarbon precursor or reactive species, thereby forming, from the fluorocarbon precursor or reactive species, at least one more desired fluorocarbon compound.

[0001] THIS INVENTION relates to the treatment of fluorocarbonfeedstocks. It relates in particular to a method of treating afluorocarbon feedstock.

[0002] According to the invention, there is provided a method oftreating a fluorocarbon feedstock, which method includes

[0003] heating, by means of radio frequency induction, a heating zone toa high temperature;

[0004] allowing a fluorocarbon feedstock, comprising at least onefluorocarbon compound, to heat up in the heating zone so that thefluorocarbon compound dissociates into at least one fluorocarbonprecursor or reactive species; and

[0005] cooling the fluorocarbon precursor or reactive species, therebyforming, from the fluorocarbon precursor or reactive species, at leastone more desired fluorocarbon compound.

[0006] The heating zone may thus be provided by a reactor. The reactormay comprise an elongate cylindrical reactor shell providing a reactionchamber which contains the heating zone, and a feedstock holder in theheating zone of the reaction chamber. The reactor shell typically is ofquartz, and may have its ends sealed off and water cooled.

[0007] The radio frequency induction heating-may be provided by a radiofrequency induction heating oven having an induction coil within whichthe heating zone of the reactor is located. In other words, theinduction heating coil is located around that part of the reactor shellcontaining the heating zone.

[0008] In one embodiment of the invention, the reactor shell-may extendvertically and be stationary. It is believed that this configurationwill be particularly suited to treating feedstock in the form ofunfilled not directly usable material as hereinafter described.

[0009] However, in another embodiment of the invention, the reactorshell may be tilted at an angle to the vertical, eg between about 5° andabout 60° to vertical, and it may rotate or vibrate. The reactor maythen be provided with a graphite crucible having transverse baffles toregulate the residence time of the feedstock in the reactor. It isbelieved that this configuration will be particularly suited to treatingfeedstock in the form of filled material, which is not directly usableas hereinafter described; as the filled material passes downwardly downthe reactor, it is depolymerized and evaporates, thus passing upwardlyout of the reactor, while filler material passes downwardly out of thebottom of the reactor. Instead, an upright reactor can be used to treatfilled material; however, the reactor will then be provided, at itslower end, with a removable plug to drain filler material.

[0010] The feedstock may, at least in principle, be in gaseous, liquidor solid particulate form, or in the form of mixtures of two or more ofthese. When the feedstock is in liquid form, it may be a more-or—lesspure feedstock comprising a single fluorocarbon compound, such as C₆F₁₄;however, it is envisaged that the feedstock will then normally be a notdirectly usable fluorocarbon product comprising two or more of a rangeof fluorocarbon compounds such as C₅F₁₂, C₆F₁₄ C₇F₁₆, C₈F₁₈, C₄F₈, C₈F₆, (C₃F₇)₃N, C₆C₁₃H, C₆F₁₂H₂, or the like. Normally, one compound willbe present in such a product as a dominant component, ie constitute themajor proportion of such a product. The feedstock may then be fed intothe reactor from the bottom. When the feedstock is in solid particulateform, it may, in particular, be a filled or an unfilled not directlyusable material such as polytetrafluoroethylene (‘PTFE’),tetrafluoroethylene hexafluoropropylene vinylidenefluoride (‘THV’),fluorinated ethylene-propylene copolymer (‘FEP’), perfluoroalkoxycopolymer (‘PFA’), or the like. By ‘filled’ is meant that thefluorocarbon feedstock may contain elements or substances such assilica, copper, carbon, etc which were originally added to fluorocarbonmaterial to impart specific properties thereto. Once such material hasbeen used and has thus become, mechanically, not directly usablematerial, but suitable for use as the feedstock in the method of theinvention, it will still contain these filling elements. In the methodof the invention, these materials are depolymerized, and the moredesirable fluorocarbon compound formed therefrom. The feedstock may thenbe fed into the reactor from the top or from the bottom.

[0011] If desired or necessary, the solid particulate feedstock may bepretreated to remove surface contaminants such as oil and dirt, eg bymeans of solvent extraction.

[0012] Typical products which may be obtained are tetrafluoromethane(CF₄), tetrafluoroethylene (C₂F₄), hexafluoroethylene (C₂F₆),hexafluoropropylene (C₃ F₆), fluorobutylene (C₄F₆), cyclicoctafluorobutylene (c-C₄F₈), decafluorobutylene (C₄F₁₀),octafluoropropylene (C₃F₈) and other C_(x)F_(y) chains where x and y areintegers.

[0013] The reactor may operate on a batch, on a semi-continuous, or on acontinuous basis. The method will thus include feeding the feedstockinto the reactor zone on a batch, on a semi-continuous, or on acontinuous basis. By ‘batch’ is meant that a predetermined quantity ofthe fluorocarbon is loaded into the reactor and allowed to react tocompletion with the hot plasma gas. By ‘semi-continuous’ is meant that ahopper is filled with feedstock, with this feedstock then being fed intothe reactor at a continuous, normally constant, feed rate until thehopper is empty, whereafter the hopper may be refilled. By ‘continuous’is meant that the feedstock is fed continuously into the reactor,normally at a more-or-less constant feed rate.

[0014] While the feedstock may, in principle, be introduced into thecavity or the first zone of the reaction chamber in any desired manner,gravity feed may, in particular, be employed since relatively largefeedstock particles can thereby readily be used, eg particles in thesize range 1 to 10 mm, preferably 3 to 5 mm. Thus, the feedstock may befed vertically into the chamber under gravity, immediately above theheating zone.

[0015] The cooling of the fluorocarbon species or precursor may beeffected in a second zone of the reaction chamber located above theheating or first zone thereof. The cooling may be effected by means of aquench probe, which may be a self-cleaning probe. The self-cleaningquench probe may comprise an outer cylindrical component mounted to thereactor, providing a central passageway and adapted to cool the hot gaspassing through the passageway; a plurality of circumferentially spacedelongate teeth or scrapers protruding inwardly from the outer componentinto the passageway; an inner cylindrical component located withclearance inside the outer component, with the inner component alsoadapted to cool the hot gas passing along the peripheral gap between thecomponents; a plurality of circumferentially spaced elongate teeth orscrapers protruding outwardly from the inner component into thepassageway, with these teeth or scrapers being staggered with respect tothe teeth or scrapers on the outer component; and drive means fordriving the one cylindrical component to oscillate relative to the othercylindrical component. The drive means may, for example, comprise aspring loaded piston driven arm.

[0016] Instead, however, any other suitable quenching means can be usedsuch as rapid expansion of the product gas, gas quenching by means ofanother gas which is cold, or the like.

[0017] The reaction chamber may be operated under pressures ranging fromnear vacuum to elevated pressures, depending on the more desiredfluorocarbon compound required as product and other process variables.Evacuation may be effected through the quench probe.

[0018] Normally a spread of fluorocarbon compounds will form asproducts. The method may then include separating the various productsfrom one another.

[0019] According to a second aspect of the invention, there is provideda quench probe which comprises

[0020] an outer cylindrical component providing a central passageway andadapted to cool a hot gas passing through the passageway;

[0021] a plurality of circumferentially spaced elongate teeth orscrapers protruding inwardly from the outer component into thepassageway;

[0022] an inner cylindrical component located with clearance inside theouter component, with the inner component adapted to cool the hot gaspassing along the peripheral gap between the components;

[0023] a plurality of circumferentially spaced elongate teeth orscrapers protruding outwardly from the inner component into thepassageway, with these teeth or scrapers being staggered with respect tothe teeth or scrapers on the outer component; and

[0024] drive means for driving the one component to oscillate relativeto the other component.

[0025] The inner component may be located centrally or concentricallywithin the outer component. The same number of teeth or scrapers may beprovided on the inner and outer components. The teeth or scrapers may bespaced equidistantly apart on their components. The teeth or scrapersmay extend parallel to one another.

[0026] The components may be hollow and/or may be provided with passagesto permit a cooling fluid, such as water, to pass through them in orderto cool or quench the hot gas.

[0027] The drive means may, as also hereinbefore described, comprise aspring loaded piston driven arm attached to one of the cylindricalcomponents.

[0028] Due to the oscillation of the one component relative to theother, cleaning of solidified or sublimated material from the surfacesthereof, on passage of the gas through the annular gap between thecomponents, is achieved.

[0029] The quench probe is particularly suited for use in a reactor ashereinbefore described; however, it is not limited only to such use.Normally, the outer component will be fixed to the reactor, with theinner component oscillating relative to the outer component.

[0030] The invention will now be described in more detail with referenceto the accompanying simplified flow diagrams.

[0031] In the drawings,

[0032]FIG. 1 shows an installation for carrying out a method of treatinga fluorocarbon feedstock, according to a first embodiment of theinvention; and

[0033]FIG. 2 shows a three-dimensional view of the quench probe of thereactor of FIG. 1;

[0034]FIG. 3 shows an installation for carrying out a method of treatinga fluorocarbon feedstock, according to a second embodiment of theinvention;

[0035]FIG. 4 shows an installation for carrying out a method of treatinga fluorocarbon feedstock, according to a third embodiment of theinvention;

[0036]FIG. 5 shows an installation for carrying out a method of treatinga fluorocarbon feedstock, according to a fourth embodiment of theinvention;

[0037]FIG. 6 shows, for TFE, a plot of reactor pressure against reactortemperature where the reactor has a fixed volume, for Example 2;

[0038]FIG. 7 shows, for FEP feedstocks, a plot of product yields againstreactor pressure, for Example 2; and

[0039] FIGS. 8 to 10 show excerpts from FIG. 7, for each of the productsshown in FIG. 7.

[0040] In FIGS. 1 and 2, reference numeral 10 generally indicates aninstallation for carrying out a method of treating a fluorocarbonfeedstock in accordance with a first embodiment of the invention.

[0041] The installation 10 includes a reactor 16. The reactor 16includes radio frequency power supply (generator) 12 having an inductionworking coil 14.

[0042] The reactor 16 also comprises a stationary quartz shell or tube18 within which is located a graphite holder or crucible 20. The reactor16 is thus of elongate form, and is located vertically upwardly.

[0043] The lower end of the quartz tube 18 is sealed off and watercooled (not shown), while a self-cleaning quench probe 22 protrudes intoits upper end. The self-cleaning quench probe 22 comprises an elongatewatercooled cylindrical outer component 24, which is fixed to thereactor 12. The outer component 24 thus has a central passageway intowhich protrudes equally spaced elongate radially inwardly protrudingteeth or scrapers 26. Inside the passageway of the outer component 24 islocated, with peripheral clearance, an elongate watercooled cylindricalinner component 28. Equally spaced elongate radially outwardlyprotruding teeth or scrapers 30 are provided on the inner component 28,with the teeth 30 being spaced circumferentially from the teeth 26. Theteeth 26, 30 may extend the full length of the components 24, 28, andthe components 24 and 28 are of substantially the same length. The innercomponent 28 is provided with drive means (not shown), such as a springloaded piston driven arm, for driving it to oscillate relative to theouter component 24 as indicated by the arrow 32. Removal of solidcontaminants from the components 24, 28 is thus achieved by means of theoscillating teeth 24, 28.

[0044] The quench probe 22 is thus a double annular water cooled probedesigned to cool the gas that forms inside the reactor 16 as hereinafterdescribed, down to below 200° C. at a rate of about 10⁵° C./second. Theprobe-is self cleaning to prevent blockages thereof since solidified orsublimated material forms on the surfaces of the probe in use.

[0045] A feedstock feed conduit 54 leads into the quartz tube 18 abovethe crucible 20, with a gravity feeder 56 connected to the conduit 54 bymeans of a pipe or conduit 58.

[0046] An evacuation flow line 31 leads from the upper end of the quenchprobe 22 to a vacuum pump 33, while a flow line 34 leads from thedischarge of the pump 33 to a compressor 36. A flow line 38 leads fromthe discharge of the compressor 36 to a product storage vessel 40. Awithdrawal line 42 leads from the storage vessel 40 to a furtherprocessing stage 44 such as a scrubber. A flow line 46 leads from theflow line 42 to a compressor 48, with the discharge of the compressor 48being connected, by means of a flow line 50, to an analytical system 52.

[0047] In use, a high temperature is created in a high temperature zoneof the reaction chamber of the reactor 18. By means of the inductioncoil 14, the crucible 20 located in the high temperature zone is thusheated by means of induction heating. When the required operatingtemperature has been reached in the heating zone, particulate solidfluorocarbon feedstock is fed into the crucible 20 by means of thefeeder 56 and the conduits 58, 54. The heat generated is sufficientlyhigh so that feedstock depolymerization occurs in the crucible 20, withthe formation of product gases.

[0048] The product gases are immediately quenched by means of the quenchprobe 22, thereby to form a more desired fluorocarbon compound which iswithdrawn along the flow line 31, 34, 38, the vacuum pump 33 and thecompressor 36 into the storage vessel 40. The product can be furtherprocessed in the processing stage 44, eg to recover a particular, moredesired fluorocarbon compound from other less desired products that areformed.

[0049] Referring to FIG. 3, reference numeral 100 generally indicates aninstallation for carrying out a method of treating a fluorocarbonfeedstock, in accordance with a second embodiment of the invention.

[0050] Parts of the installation 100 which are the same or similar tothose of the installation 10 hereinbefore described, are indicated withthe same reference numerals.

[0051] In the installation 100, the quartz tube or shell 18 of thereactor 16 is tilted at an angle of between 5° and 60° to the vertical,and is fitted with a graphite crucible 20, having transverse, egcircumferential, internal baffles (not shown). The tube 18 rotates orvibrates. The feedstock enters the upper end of the tube 18 whiledepolymerized gases, ie product gases, exit from the lower end thereof.Extracted filler material passes out of the bottom of the tube 18, asindicated by arrow 102.

[0052] Referring to FIG. 4, reference numeral 150 generally indicates aninstallation for carrying out a method of treating a fluorocarbonfeedstock, in accordance with a third embodiment of the invention.

[0053] Parts of the installation 150 which are the same as or similar tothose of the installations 10, 100 hereinbefore described, are indicatedwith the same reference numerals.

[0054] In the installation 150, a liquid feedstock supply 152 isprovided. A flow line 154 leads from the supply 150 into the bottom ofthe quartz tube 18 of the generator 12 and into a bed 156 of graphitegranules.

[0055] Thus, in use, the graphite bed 156 is heated by means of theinduction coil 14. Liquid feedstock is fed into the bottom of thecrucible, passes upwardly through the graphite bed, and is heated anddissociated as hereinbefore described.

[0056] Referring to FIG. 5, reference numeral 200 generally indicates aninstallation for carrying out a method of treating a fluorocarbonfeedstock, in accordance with a fourth embodiment of the invention.

[0057] Parts of the installation 200 which are the same as or similar tothose of the installations 10, 100 and 150 hereinbefore described, areindicated with the same reference numerals.

[0058] The installation 200 includes a hopper 202 for solid particulatefeedstock. The hopper 202 is mounted to a screw feeder 204 whosedischarge is connected, by means of a conduit 206, to the bottom of thequartz tube 18.

[0059] Thus, in use, solid particulate feedstock is fed upwardly fromthe bottom of the reactor 12. As the solid particulate feedstock is fedin an upwardly direction through the reactor 16 and the graphitecrucible 20, it reaches the high temperature heating zone of thereactor, dissociates and is then quenched by the probe 22, ashereinbefore described.

[0060] In the Examples, a 10 kW, 800 kHz radio frequency generatoroperated at 8 kW in accordance with the installation 10 of FIG. 1 wasused. The stationary quartz tube 18 of the reactor 16 had a nominaldiameter of 70 mm and a length of 300 mm. The system was evacuatedthrough a filter (not shown), by means of a high integrity dry vacuumpump 32. All pressures are indicated in kPa(a) while product yields arerecorded as relative volume percent.

EXAMPLE 1

[0061] The installation 10 was operated on a continuous basis, withabout 2 kg/h of particulate unfilled or spent PTFE material being fedcontinuously into the crucible 20.

[0062] It was found that the reactor 16 needed to be evacuated to arelatively high vacuum in order to yield a maximum amount of TFE. Fordifferent product compositions, different feedstock materials andprocess parameters will be required. Specific pressure and temperatureranges will be characteristic to the product composition required. Thus,to depolymerize PTFE and obtain TFE as the principal product, a reactiontemperature of 400° C. to 700° C. and a sub-atmospheric pressure isrequired in the reactor 16.

[0063] It was found that a heating up period of approximately 5 minuteswas required to reach the operating temperature of 400° C. to 700° C.During this time, some feedstock was present in the crucible 20,although the feeder was not yet activated. This feedstock softened andbegan to depolymerize. When the operating temperature had been reached,the feeder 26 was activated to provide the throughput of about 2 kg/h.If desired, the throughput can be varied between 1 kg/h and 10 kg/h feedmaterial for a 10 kW installation.

[0064] At an operating temperature of 400° C. to 700° C. and asub-atmospheric pressure of about 1 kPa immediate depolymerization ofthe PTFE by means of pyrolysis, took place, with the PTFE beingvaporized and broken down into fluorocarbon precursors or reactivespecies. These precursors or reactive species were immediately quenchedby means of the quench-probe 22, to produce TFE. Due to therepolymerization of the TFE gas, accumulation of a finely divided whitepowder on all the cold surfaces of the reactor 16, was observed. Thiswas subsequently cleaned by the self-cleaning quench probe.

[0065] The results obtained are set out in Table 1. TABLE 1 AnalyticalResults Products Example 1 - Product gas CF₄ (%) — C₂F₆ (%) 0.062 C₂F₄(%) 83.9 C₃F₆ (%) 6.83 c-C₄F₈ (%) 9.01

[0066] PTFE was successfully depolymerized in this example at about 1kWh/kg PTFE. No major process parameter and hardware scale-up problemsare envisaged.

[0067] The installation or system 10 was particularly set up to handlenot directly usable PTFE material to supplement the production of TFE(C₂F₄) which is a precursor for the manufacture of other complexfluorocarbons, eg c-C₄F₈. This processing can be performed in theprocessing stage 44.

[0068] Table 1 indicates that surprisingly high yields of C₂F₄ wereobtained, considering that the configuration of the installation 10 hadnot been optimized.

EXAMPLE 2

[0069] In this example, the conversion of FEP (FluorinatedEthylene-Propylene copolymer) scrap material into usable high qualityproducts such as TFE (tetrafluoroethylene), HFP (hexafluoropropylene) orc-C₄F₈ (cyclic octafluorobutylene) was explored as a function of reactorpressure, for two distinct temperature profiles.

[0070] During preliminary test runs it was found that the reactionefficiency and the products formed are sensitive to both reactorpressure and crucible temperature. As a reference to guide the pressuredependency tests, another preliminary run was first performed. In thispreliminary run, a closed container of a fixed volume having temperatureand pressure measurement probes inside was utilized to heatincrementally a fixed amount of TFE through a temperature gradient whilerecording the gas pressure as a function of temperature. FIG. 6 wasderived from this information. FIG. 6 shows a series of humpssuperimposed on a gradually increasing background of an ordinary P/T atconstant volume curve. This shows the formation of different products atdifferent temperatures with the corresponding pressure changes as thevolume (number of molecules) changes. During a recombination reactionthe pressure drops and during a dissociation reaction the pressurerises. Careful examination of the pressure slopes in conjunction withavailable reaction information enabled the identification of thedominant product for each temperature region. These are also indicatedin FIG. 6. TFE for example starts to recombine to form c-C₄F₈ at atemperature of 270° C. In turn c-C₄F₈ starts to dissociate at atemperature of 450° C. and forms HFP. These products are stable whenquenched. Since the production of HFP was the predominant goal in thesubsequent test runs, the crucible temperatures were accordingly chosenin the vicinity of 600° C.

[0071] For these subsequent test runs, the installation 10 of FIGS. 1and 2 was again operated on a continuous basis while FEP was fedcontinuously into the crucible (ID=54 mm, OD=64 mm, length=180 mm) whereit was melted and chemically cracked. The coil around the crucible wasmodified to heat the crucible non-uniformly to create a temperatureprofile which increased from bottom to top. This was done, firstly, toprevent condensation of liquid or solid product before the quench probewas reached. Secondly, since the depolymerization reaction substantiallytakes place at the bottom of the crucible (lower temperature end), theupper end of the crucible must be hotter to ensure complete sublimationof the vapor.

[0072] Thirdly the hot zone serves as a preheating zone for the FEPparticles as they are fed into the crucible. During the first run thecrucible was operated between 630° C. and 830° C. with the center at710° C., the run being designated as “630° C.”. The second run wasoperated between 600° C. and 780° C. with the center at 700° C., andaccordingly designated “600° C.”. The results are given in Table 2.TABLE 2 Pressure 20 30 50 60 80 100 120 630° C. TFE 52 30 25 17 HFP 3850 52 64 cC₄F₈ 10 17 18 14 600° C. TFE 62 47 33 25 23 HFP 32 37 41 42 44cC₄F₈ 5.4 17 27 28 28

[0073] TABLE 3 Energy In (kW) 4 Enthalpy (kWh/kg) 1.6 Mass Flow FEP(kg/h) 2.4 Run duration (h) 4 C₂F₄ (kg/h) 1.04 C₃F₆ (kg/h) 0.782 c-C₄F₈(kg/h) 0.31 Fluorine balance 100% Total Mass Balance  89%

[0074] The results of Table 2 are represented graphically in FIG. 7 fromwhich the pressure and temperature dependence of the product yield isevident. FIGS. 8-10 represent excerpts from FIG. 7, one for each of theproducts. Table 3 sets out the operating conditions, fluorine balanceand a total mass balance. In respect of the total mass balance of 89%,the 11% mass loss is mainly due to solids forming on the cold surfaces.

[0075] Generally, FIG. 7 shows that as the pressure increases the yieldof TFE decreases (see also FIG. 8), c-C₄F₈ moves through a maximum (seealso FIG. 9) and HFP increases (see also FIG. 10). The latter two show amarked temperature effect in the sense that the higher crucibletemperature profile yielded significantly more HFP and less c-C₄F₈. Itis believed that the product gas retention time at the higher crucibletemperature is long enough to form more HFP by decomposition of c-C₄F₈.In contrast, a much milder temperature effect is observed for TFEproduction (FIG. 8). This is probably due to the fact that in both runsthe TFE production at the respective temperatures in the crucible hasbeen completed (see FIG. 6) by the time the gas reaches the quench probeand what is-observed here is its dissociation rate into the twosuccessive products, the selectivity of which depends on the crucibletemperature.

[0076] From the foregoing it is obvious that by further standardexperimentation temperature and pressure parameter sets may be generatedto optimally control the selectivity of at least the majority of desiredproduct combinations. It is also obvious that the process could beextended to include the conversion of liquid not-directly usablefluorocarbon feed stocks.

[0077] This method of converting FEP into useful products proved to beinexpensive, safe, environmentally clean, versatile and easy to operate.Combined with a well developed distillation plant high purity, highquality and high value products can be produced.

[0078] Typical products that can be obtained with the method of thepresent invention are C_(x)F_(y) chains, where x and y are integers. Insuch chains, when directed to TFE production, the main product isapproximately 90% TFE.

[0079] It was found that the induction generator 12 is very efficientwith little energy being lost to surroundings. The installation 10 has avery short start-up time.

[0080] Advantages of the method of the present invention are that nocarrier gas is required, and that the product obtained is relativelypure. Thus, only a relatively simple distillation stage is normallyrequired for separating the resultant TFE from the other productsobtained.

[0081] By the method of the present invention, filled and unfilled notdirectly usable fluorocarbon materials can be depolymerized andtransformed into relatively pure, high value products by means ofpyrolysis, with a minimal downstream distillation requirement.

1. A method of treating a fluorocarbon feedstock, which method includesheating, by means of radio frequency induction, a heating zone of areaction chamber to a temperature not exceeding 950° C.; allowing afluorocarbon feedstock, comprising at least one fluorocarbon compound,to heat up in the heating zone; choosing a reaction chamber pressure anda heating zone temperature so that the fluorocarbon compound dissociatesor depolymerizes into at least one more desired fluorocarbon compound;forming a hot product gas comprising the more desired fluorocarboncompound; and quenching the hot product gas to stabilize the moredesired fluorocarbon compound.
 2. A method according to claim 1, whereinthe reaction chamber is provided by a reactor comprising an elongatecylindrical reactor shell, with the reaction chamber containing theheating zone, and with a feedstock holder being provided in the heatingzone of the reaction chamber.
 3. A method according to claim 2, whereinthe radio frequency induction heating is provided by a radio frequencyinduction heating oven having an induction coil within which the heatingzone of the reactor is located.
 4. A method according to claim 2 orclaim 3, wherein the reactor shell extends vertically and is stationary.5. A method according to claim 2 or claim 3, wherein the reactor shellis tilted at an angle to the vertical and rotates or vibrates.
 6. Amethod according to claim 5, wherein the reactor is provided with agraphite crucible having transverse baffles to regulate the residencetime of the feedstock in the reactor.
 7. A method according to any oneof claims 2 to 6 inclusive, wherein the fluorocarbon feedstock is inliquid form, is a pure feedstock comprising a single fluorocarboncompound or is a not directly usable fluorocarbon product comprising twoor more fluorocarbon compounds, with one compound being present in theproduct as a dominant component so that it constitutes a majorproportion of the product, and is fed into the reactor from the bottom.8. A method according to any one of claims 2 to 6 inclusive, wherein thefluorocarbon feedstock is in solid particulate form, is a filled or anunfilled not directly usable material, which has optionally beenpretreated to remove surface contaminants, and is fed into the reactorfrom the top or the bottom.
 9. A method according to claim 8, whereinthe fluorocarbon feedstock is introduced into the reaction chamber byfeeding it vertically and under gravity into the reaction chamber,immediately above the heating zone and wherein the feedstock particlesare in the size range 1-10 mm.
 10. A method according to any one ofclaims 2 to 9 inclusive, wherein the quenching of the hot product gas iseffected in a second zone of the reaction chamber located above theheating or first zone thereof.
 11. A method according to claim 10,wherein the quenching is effected by means of a self-cleaning quenchprobe.
 12. A method according to claim 11, wherein the self-cleaningquench probe comprises an outer cylindrical component mounted to thereactor, providing a central passageway and adapted to cool the hot gaspassing through the passageway; a plurality of circumferentially spacedelongate teeth or scrapers protruding inwardly from the outer componentinto the passageway; an inner cylindrical component located withclearance inside the outer component, with the inner component alsoadapted to cool the hot gas passing along the peripheral gap between thecomponents; a plurality of circumferentially spaced elongate teeth orscrapers protruding outwardly from the inner component into thepassageway, with these teeth or scrapers being staggered with respect tothe teeth or scrapers on the outer component; and drive means fordriving the one component to oscillate relative to the other component.13. A quench probe which comprises an outer cylindrical componentproviding a central passageway and adapted to cool a hot gas passingthrough the passageway; a plurality of circumferentially spaced elongateteeth or scrapers protruding inwardly from the outer component into thepassageway; an inner cylindrical component located with clearance insidethe outer component, with the inner component adapted to cool the hotgas passing along the peripheral gap between the components; a pluralityof circumferentially spaced elongate teeth or scrapers-protrudingoutwardly from the inner component into the passageway, with these teethor scrapers being staggered with respect to the teeth or scrapers on theouter component; and drive means for driving the one component tooscillate relative to the other component.
 14. A quench probe accordingto claim 13, wherein the inner component is located centrally within theouter component; and/or wherein the same number of teeth or scrapers areprovided on the inner and outer components; and/or wherein the teeth orscrapers are spaced equidistantly apart on their components; and/orwherein the teeth or scrapers extend parallel to one another.
 15. Aquench probe according to claim 13 or claim 14, wherein the componentsare hollow and/or are provided with passages to permit a cooling fluidto pass through them in order to cool or quench the hot gas.
 16. Aquench probe according to any one of claims 13 to 15 inclusive, whereinthe drive means comprises a spring loaded piston driven arm attached toone of the cylindrical components.
 17. A novel method of treating afluorocarbon feedstock, substantially as described and exemplifiedherein.
 18. A novel quench probe, substantially as described andillustrated herein.